She denied that someone had hacked into the system, explaining that the message was manually added to the system by an employee.

"We've launched an investigation to see what consequences this will have."

She refused to comment on whether the person behind the text had been identified, or whether they would be fired.

Stephan added that the "Nazi receipts" had only been found at the one Stockholm store, and that only two were printed out.

The story on Aftonbladet, Sweden's biggest newspaper, shot to top of the most-read section and has been shared 14,000 times on Facebook.

The news comes just days after the nationalist Sweden Democrats, led by Jimmie Åkesson, doubled their support in the national election, grabbing 12.9 percent of the Swedish votes to become the country's third largest political party.